Pump



T. V. DILLSTRM Dec. 3, 1940.

PUMP

Filed May 2e, 1939 1o sheets-sigan 1 O ,4f 3 Z 7.

1..v. DILLSTROM Dec. 3, 1940.

' PUMP Filed May 26, 1939 10 Sheets-Sheet 2 IIIVL lllllll Il m/ENTO 180 GAM Ro TA T/o/v De@ 3 194@ T. v. DILLSTRM Y 2,223,755

v y PUMP Filed May 26, 1939 l0 Shee'Ls--Sheekl 3 INVENTOR.

ATTORNEY.

Dwi 3 1940- T. v. DILLs'rRM 2,223,755

` l PUMP Filed May 26,r 1939 10 Sheets-Sheet 4 ABY MQW

ATTORNEY T. V. DILLSTRM PUMP Filed May 26, 1939 10 Sheets-Sheet 5 ATTORNEY.

Dec. 3, 1940. T v D|| 5TRM l 2,223,755

PUMP

Filed May 26, 1939 10 Sheets-Sheet 6 Y .fg/c9226'.

DEL /VERY PEE/o0 Ffa-w- INV NTOR.

u- ATTORNEY.

D 3, 1940- T. v. DILLsTRoM 2,223,755

PUMP Filed May 26, v19159 10 Sheets-Sheet 7 INVI'VT ffm Lw M M TTORN EY.

D- 3 1940- 1'. v. DlLLsTRM 2,223,755

PUMP 4 Filed May 26, 1939 10 Sheets-Sheet B Dec. 3, 1940. T. v. DILLsTRM 2,223,755

PUMP l Filed May 26, 1939 10 Sheets-Sheet 9 vrl 141111111101111.-

Ja (vfm/ FaQ/00 #1 aan/@2f if? Ma MATTORNEY.

Dn 3 B94@ l T. v. DILLSTRM 2,223,755

PUMP

Filed May 25, 19:59 10 sheets-Sheet l0 Patented Dec. 3, 1940 n PUMP Torbjrn Viktor Stockholm, Sweden, l assignor to H andeisaktiebolagct Vidar, Stockholm, Sweden, a corporation of Sweden Application May 26,' 1939, Serial No. 275,974

In Sweden April 6, 1939 Zo'Ciaims.

This application is a continuation in part with respect to my copending application Serial Number 224,211.led August 10, 1938, and relates y back thereto, as toall common subject matter, 5 for all dates and rights incident to the :Bling thereof and to the filing of corresponding fori very high pressure, they must act with extremev accuracyand precision, they must be capable of adjustment to vary the quantity of fuel de- 20 livered per cycle of .operation and they must,v

when supplying fuel to a multiple cylinder .engine, be capable of delivering, as nearly as possible, precisely the same quantity of fuel to each outlet forany given setting of pump capacity.

In order to meet these extremely rigid requirements, the m'ostsatisfactory type of pump Y arrangement heretofore developed has been that in which a separate cylinder and plunger is provided for each injector or other device to which 30 fuel must be supplied and because of the extreme accuracy with which such pumps must be manufactured and the pressures involved, such pumps havek proved to be very expensive to manufacture and also diftlcult to maintain in proper 35 adjustment over long periods of service so that appreciable variation is not developed, through wear or other causes, in the quantities of fuel delivered to different outlets leading for example izo-'injectors in different cylinders of the same engine.

ftis the general object of the present inventionto improve upon piorcforms of construcftion of plunger pumps and to provide novel plunger pump structure which will enable liq- 45 uids such as fuel oil to be supplied to a pluralityof points of consumption with great laccuracy of control both as to the quantity delivered and the relation of the quantities delivered by the pump to different outlets, while at the same 50 time accomplishing the desired results with pump structuren/'ery much more simple and inexpensive than structures heretofore representingthe best available for accomplishing the desired B11113058- To this eind the invention contemplates the provision of improved plunger pump structure so constructed that liquid is delivered to a plurality of 'outlets from a common pump chamber through the action of a single plunger.

The manner in which the above general object, and other and more specic objects of the invention to be hereinafter pointed out. are attained, will best be understood from a consideration of the ensuing portion ofthis specification, taken in conjunction with the accompanying drawings, in which is described various forms of constructions! examples of pump structure forcarrying the invention intoeiiect.

In the drawinga'Fig. 1 is a transverse section of a pump embodying the invention. taken in `part along the line I--I of Fig. 2 and in part along line I-I of Fig. 3:

Fig. 2 is a fragmentary line 2--2of Fig. 1; l

Fig. 3 is a section taken on the line 3-3 of 2o F1a. 1; T

Fig. 4 is'a section taken on the line H of Fig- 1:

Fig.. 5 is a section taken on the line 5-5 of Fig. 4;

Fig. 6 is an enlarged view of part of the pump plunger and barrel shown in Fig. 1, certain passages being turned into the plane ofthe drawing for clarity of illustration I l Fig. 7 is a developed view of the plunger and barrel surface of the pump shown in Fig. 1 with the plunger adjusted for maximum delivery;

Fig. 8 is 'a series of diagrams illustrating various phases', of operation during the delivery stroke of the type of pump shown in, Fig. 1. only two outletsl being shown in the diagrams, however, for the sake of simplicity;

Fig. 9 shows vdifferent phases of the delivery stroke of a different form of plunger applicable for use in a pump of the general kind shown in Fig. l:

Fig. 10 illustrates a diiferent arrangement of outlet openings in a pump of the general kind shown in Fig. 1; l

Fig. 11 illustrates in developed form the control portion of the plunger sm'face shown in Fig. 7, but in partial load position' of adjustment;

Fig. 12 is a view similar to Fig. 11 showing a ditrerent form of control ,surface on the pump plunger for effecting a diiferent modev of timing of part load delivery with respect to the timing of the pump actuating mechanism: A l

Fig.. 13 is a/view similar to Fig. 12 showing 4 still another form' of pump control section taken on the I Fig. 17 is a view similar to Fig. 16 showing still another overflow arrangement;

Fig. 18 is a partial section showing a different form of pump plunger and barrel construction for use in a pump of the kind shown in Fig. 1:

Fig. 19 is a central longitudinal section of the pump barrel of Fig. 18, taken on the lines I9-I9 of Figs. 18 and 20;

of Fig. 19;

Fig. 21 is a section taken on line 2I-2I of Fig. 19;

Fig. 22 is a series of diagrams illustrating different phases of delivery stroke operation of the plunger of the type shown in Fig. 18, only two outlets again beingJ shown in these diagrams for the sake of simplicity;

Fig. 23 is a developed view of part of the barrel and plunger surfaces of the pump shown in Fig. 18;

Fig. 24 is a fragmentary section similarto Fig. 1 showing a pump having the same type of plunger as lshown in'Fig. 18 combined with a different'form of tappet construction;

Fig. 25 is a diagram` similar to Fig. 8 showing another form of cylinder porting arrangement;

Fig. 26 is a diagram similar to Fig. 25 showing still`another porting arrangement providing pre- D- compression of fuel before delivery; v

Fig. v2'7 is a diagram similar to Fig. 26 showing an arrangement providing variable4 degrees of precompression;

Fig. 28 is a diagram similar to Fig.- 27 but 46 showing a different variation of precompression with respect to load adjustment of the pump;

Fig. 29 is a diagram illustrating a different form of plunger porting construction;

Fig. 30 is a diagram illustrating the features 50 of Fig. 25 applied to a different form of plunger; Fig. 31 is a diagram illustrating still another plunger porting arrangement;

Fig. 32 is a diagram similar to Fig. 31 showing a different arrangement for part load control; Figs. 33 and 34 are diagrammatic sectional and developed views of still another arrangement providing for precompression with a plunger of the general type shown in Fig. 30;

Figs. 35 and 36 are diagrammatic sectional and 60 ,developed views respectively showing an arrangement providing for variable precompression with a plunger of theftype shown in Fig. 33;

Fig. 37 is a fragmentary section similar to Fig.

6 showing a different manner of locating the de- 05 livery ports; l 1

Fig. 38 is a developed view of the structure shown in Fig'. 37; f

Fig. 39 is a view similar tol Fig. l, partly in` elevation, showing a type of plunger and cylin- 70 der porting different from the preceding embodimen s;

Fig. 40 is a section taken on the line 40-40 of Fig. 39;

- Fig. 41 is a section taken on the line II-II oi' 76 Fig. 39;

2,228,755 effecting yet another mode of timing of part' Fig. 20 is a top plan view taken on line 2li-2li Fig. 42 is a section taken on the line 42-42 of Fig. 41; Y i

Fig. 43 is a fragmentary section on enlarged scale of the pump and barrel arrangement of Fig. 39, certain of the passages being moved into the plane of the section for clarity;

Fig. 44 is a developed view of the plunger and cylinder barrel surfaces shown in Fig. 43;

Fig. 45 is a series of diagrams illustrating a different embodiment of thel general type of barrel and plunger structure shown in Figs. 39

to 44, and showing the plunger in various positions on its discharge stroke;

Fig. 46 is a developed view on enlarged scale of plunger and .cylinder surfaces 'of the kind shown in Fig. 45;

Fig. 47 is a section showing a form of pump of the general type shown in Fig. 45 but arranged with the cylinder delivery ports at the same level in the pump barrel;

Fig. 48 is a developed view of the device shown in Fig. 47; A

Fig. 49 is a series of diagrams showing the plunger of Fig. 47 in different positions on its discharge stroke;

Fig. 50 is a fragmentary section showing a form of pump in which a pump suction valve is eliminated and the pump through the overflow passage; and

Fig. 51 is a series -of diagrams showing the plunger of Fig. 50 in diiferent positions during its discharge stroke.

Referring now more particularly to Figs. 1 to 5, the pump illustrated is a single cylinder pump adapted to supply liquid fuel to four separate places of consumption Ysuch as fuelv injectors. The pump comprises a casing part Ill in the base portion of which there is mounted a cam shaft I2 adapted to be driven from any suitable source of power and carrying cam IB which may be integral with or fixed to the shaft. At the top of the casing part I0 there is secured a head part I6, which is advantageously removably fixed to part I0 by a number of bolts, one of which is shown at I8.

'Ihe pump cylinder or barrel 20 is, in the embodiment illustrated, detachably secured Ato the head I6 by means of a threaded clamping collar 22 and is prevented from rotating with respect to the pump body by means of4 a locating pin 24. 'I'he pump plunger 26 is reciprocably mounted in the bore of barrel 20 and head I6 is bored out in alignment with the bore of the barrel to pro- Vvide a pump chamber 26 with which the suction or supply conduit 30 communicates. Between the conduit 30 and the chamber 28 there is located the non-return suction valve which in the chamber lled form shown is a spring loaded ball valve 32. It.

is to be noted in this connection that the ow of liquid to the pump chamber from the suction line is through a straight channel substantially unobstructed except for the suction valve. This overflow passage 34 formed partially in the barrel and partially inthe head part of the pump casing.

The pump barrel is further provided with four outlet or delivery ports located in a zone above y vertical slot 'I4 in the segment 68. Pin 12 passes the overflow ports and advantageously distributed so as to open into the bore of the barrel in different axial planes passing through the axis of the bore. These delivery ports, like the relief ports, are distributed in longitudinally spaced relation along the pump barrel. One of these ports d1 is shown in Fig. 1 and the remaining three ports, dz, da, d4, appear in Fig. 5.

The ports Z1-d4 are connected respectively by delivery passages 36, 38, 40 and 42 to individual delivery'conduits 36a, 38a, 40a and 42a. Each of the several delivery passages is provided with a spring loaded discharge valve, the one controlling passage 36 being indicated at 44 in Fig. l.

In the embodiment illustrated the several delivery ports are displaced peripherally with respect to adjacent ports by 90 andthe line of relief ports is also displaced peripherally with respect to twol peripherally adjacent delivery ports (see Fig. 3). As will hereinafter more fully appear, the arrangement of the outlet ports peripherally of the barrel may be varied without aiecting pump operation.

The pump plunger is provided with two longi tudinally separated recesses 46 and 48; both of which are in constant communication with the pump chamber 28 by means of a central longitudinal bore 50 in the pump plunger, which at one end opens into the pump chamber and which is placed in communication with the surfaces of the recesses by one or several transverse bores 52 and 54 respectively.

I In the embodiment illustrated, the recess 46 encircles the periphery of the pump plunger while the recess 48 is provided with a special configuration to be described later.

Between the plunger and the cam there is provided altappet 56 mounted for reciprocation in a suitable bore in the casing part I8 and at its lower end provided with a'roller 58 contacting the face of the cam. 'I'he tappet is restrained against turning movement in the casing by means of a locating pin 60 the inner end of which engages a suitable vertical slot 62 in the tappet. The upper portion of the tappet is of cup-like form providing a cylindrical recess into which the lower end of the pump plunger extends and against the bottom of which recess the enlarged foot 26a of the plunger rests. The foot 26a advantageously is formed with a convexly curved bottom surface as shown in Fig. 1. 'I'he bore of the tappet is shouldered to provide a seat for a retaining washer 64 through which the plunger passes and which engages the upper surface of the foot 26a to prevent axial displacement of the plunger with respect to the tappet.

. The retainer 64 is held in place by the pump plunger spring 66 which is compressed between this retainer and the collar 22. As will be evident from Fig. 1, spring 66 operates to cause the tappet and the pump plunger to follow the path of travel determined by the. profile of cam I4.

Adjustment of the quantity of fuel discharged by the pump is effected by turning the-pump plunger about its axis and in order to effect this control, a segment 68 isy provided having teeth engaging the rack l0 slidably mounted for movement axially of itself in the pump casing. Rack 'i8 projects from the pump casing for connection to any suitable control for manual or automatic adjustment of the delivery capacity of the pump. Turning movement imparted to segment 68 by movement of rack 10 is transmitted to the pump plunger by means of a pin 12 fixed at one end in the plunger and at its other end sliding in a flow recess 48.

through an arcuate slot I6 in the wall of the tappet, which permits the pin to be turned by rack 18 while the tappet remains rotationally stationary.

Referring now more particularly to Figs. 6 and 7, in which the pump cylinder and plunger arrangement shown` in Fig. 1 has been shown on enlarged scale and in developedform for clarity, the plunger 26 has been shown in its position of rotational adjustment for full load operation.

Recess 46, whichV may conveniently be considered as the delivery recess, also constitutes a port in the plunger, dened by edges 46a and 46h, which port is conveniently designated as a plunger delivery port to distinguish it from the delivery ports di-di, which are conveniently designated ascylinder delivery ports.

Recess 48, which may conveniently be considered as the overflow recess, has upper and lower limiting edges 48a and 48e and between and spaced from these edges there is provided a control portion 48' 'in the form of an island-like projection which extends partially around the circumference of the plunger and the surface of which is in contact with the wall of the cylinder bore. The controlportion 48' provides two parallel transverse control edges 48h and 48d which operate, as will hereinafter more fully appear,

to control the beginning and ending of full load delivery periods, and a third inclined edge 48o which in the embodiment illustrated merges at l'one end with edge 48b and operates to control munication with the pump chamber, which channel constitutes a relief or overflow port in the plunger which is conveniently designated as a vplunger overflow port to distinguish it from the cylinder overflow ports n n. Likewise, a channel 489. constituting a second plunger overflow port longitudinally spaced from the one formed by channel 48j and also in constant communication with the pump chamber, is formed by the space between edges 48d and 48e.

Referring now more particularly to Fig. 8, which shows the plunger in various positions on its delivery stroke and in which for the sake. of convenience only two relief or overow ports ri and r2, and two delivery ports di and d2, have been shown, it is assumed that the pump chamber 28 is lled with liquid drawn thereinto from the suction conduit 38 by the preceding suction stroke of the plunger.

In position 8a,.the plunger is assumed .to be at the bottom of its stroke and about to ascend on its delivery stroke. In this position, the recess 48 is not in communication with any delivery port while the channel 48j, forming a part of the recess 48, is in communication with the relief port r1 so that movement of the plunger on its delivery stroke is permitted by overflow of liquid from the pump chamber through the bores 58 and 54 in the plunger and through the over- In position 8b, the' plunger has inoved upwardly until the upper control edge of the delivery recess 46 is just passing the lower edge of the delivery port d1, to place port d1 in comiro munication `with the pump chamber by way of i sition, channel 48j is still in communication with relief port r1 so that when edge 46a passes the lower edge of port di to establish delivery communication, delivery does not thenl take place because of the open overflow connection through the relief port.

When the plunger reaches the position 8c, the delivery port d1 has been substantially opened and when the plunger reaches this position, delivery commences due to the channel 48j having passed out of communication with the relief port r1. This determines the instant of commencement of delivery and with the plunger in the full load position of rotation shown, which corresponds to the position shown in Fig. 7, it will be evident that commencement of injection is determined by the control edge 48h.

Continued movement of the plunger from the position shown at 8c to the position shown at 8d effects delivery through portdl which, it will be noted, is in communication with the delivery recess' 46 during this period of movement of the plunger. When the plunger reaches the position 8d, the overflow channel 48g comes into communication with the relief port r1 to terminate the delivery period and again by reference to Fig. 'I it will be evident that the end of the delivery period will be determined' bylthe control edge 46d. Thus the delivery through the port d1,

which may be termed delivery period No. 1, occurs during movement of the plunger from position 8c to position 8d. Also, it will be noted thatthe delivery recess 46 is in communication i with the delivery port d1 both immediately before and immediately after the delivery period. Stated in another way, the overow periods immediately preceding and immediately following the delivery period overlap the terminal portions of the period when the plunger delivery port is in communication with the cylinder delivery port, the actual delivery period being shorter than the period of communication between these two deliveryports. Thus the pump chamber is temporarily placed in simultaneous communication with a, delivery passage and an overflow passage just before actual delivery commences and just after it ceases. y

In the position 8e, the edge 46h of the delivery recess passes the upper edge of delivery port d1, overflow continuing to take place during the movement from position 8d to position 8e by the continued communication between overflow channel 48g and relief port n. Before channel 48g passes outA of communication with port r1, channel 48j comes into communication with port n', and during continued movement of the plunger through positions 8f and 8g, overow continues through both ports n and r2. When positionh 1s reached, the, delivery recess 46 is about to come into communication with the delivery port d2 because of edge 46a passing the lower edge of this port, and relief channel 48g passes out of communication with relief port r1. Between positions 8h and 8i, the delivery port dz is brought into communication with the delivery recess 46, but noinjection takes place during this movement because of the continued communication of overflow channel 48j with relief port r2 after the overilow channel 48g has relief port r: and channel 48g is already out of communication with relief port n.

vDelivery continues until relief channel 48g comes into communication with relief port rz as shown at position 81', communication between channel 48g and port rz continuing until the delivery recess 46 passes out of communication with port da (position 8k) and to the end of the movement of the pump plunger in the direction of its delivery stroke, as shown in position 8l.

It will be noted that in order tov secure the desired continuity of overflow between delivery periods the overflow through the two channels 48j and 48g overlaps, resulting at certain periods in simultaneous overflow through both of these ports are located in a zone in the pump barrel nearer to the pump chamber end of the barrel than is the zone in which are located the relief ports. It is, however, immaterial which group of ports is nearer the pump chamber end of the barrel and the reverse of the arrangement shown in Figs. l to 8 has been indicated in Fig. 9, in which the relief ports r1 andv r2 are located in a zone nearer to the pump chamber while the delivery ports d1 and da are located in a zone further from the pump chamber. Obviously, if

, the positions of the groups of cylinder ports are reversed, the positions of the delivery and overow recesses in the pump plunger Amust also be reversed as indicated in Fig. 9. For purposes of illustration the pump plunger in Fig. 9 has been shown in two positions, b and c, corresponding to the positions b and c of Fig. 8 and illustrating the approach to and commencement of the first delivery period.

It will be apparent that any cylinder delivery port may be at any place on a given circumference lying in a. plane-normal to the axis of the cylinder bore without affecting the timing of delivery through the port. In some instances it may be desirable to provide for simultaneous delivery to two or more outlets, and as will beappreciated from Fig. l0, this may readily be e accomplished by placing one or more additional delivery ports, such as d and d", in the same location longitudinally of the cylinder bore as delivery ports d1 and d2, respectively, so that simultaneous delivery may be made through a plurality of delivery ports during each delivery period rather than through a single port.

Referring again to Fig. 7, and having in mind the sequence of operations during the delivery stroke explained in .connection with Fig. 8, it c will be evident that for any delivery period, as for example the delivery period through port di, the commencement of the delivery period is de terminedby the control edge 48h closing relief port r1 and the end of the delivery period is determined by the control edge 48d opening this relief port. With the plunger in the position of ro tation shown in Fig. 7, the distance between these control edges is maximum and consequently with the plunger in this position, these edges determine `the maximum period of delivery. Further, as long as the plunger is in any position oi rotation where these parallel edges are controlling, the length of the delivery period will be constant and 5 the relation of the beginning and end of the delivery period will not vary with respect to the positions of rotation of the cam shaft of the pump. If, however, the plunger is rotated to bring` the control edge 48e to a position where l0 it passes portn, as shown in Fig. 11, it will be position determined by edge 48h, while the position of the plunger at which the relief port is opened by edge 48d remains unaltered. -Stated in terms of fuel injection to an engine, this arrangement operates upon adjustment for part" load to commence injection at a later time in the cycle of operation of the pump, and consequently at a later time in the cycle of engine operation, while maintaining the end of the injection period constant with respect to the cycle'of pump operation.

2 5 For some types of engines it may be desirable to maintain the commencement of injection constant with respect to the engine cycle insofar as adjustment of the pump for variations in load is concerned. In order to accomplish this, the arrangement of the control edges may be as shown in Fig 12, in which the edge 48e for part load control is inclined oppositely as compared with Fig. 1l. With this arrangement, the'control edge 3,5' 48h closes port n with the pump cam in the same position of rotation regardless of load adjustment of the plunger. At partV load adjustment, however, as shown in Fig. 12, the inclined edge portion opens the relief port earlier in the delivery stroke than would be the case for full 40 load adjustment, in which latter case ledge 48d would control the opening of the overow.

In Fig. 13, still another arrangement of partl load control edge is illustrated, which operates to retard the time of closing of the relief port with respect to the pump cycle when part load adjustment is eiected, and to advance the time of opening of the relief port with respect to the pump cycle when in this position of adjustment.

The arrangement in Fig. 13 in eifect combines the arrangement shown in Figs. l1 and 12. From the foregoing it will be evident thatin a pump embodying the present invention, substantially any timing variation of part load injection with respect to the operation of the eng'iri'e t0 which fuel is being supplied by the pump .may be effected by suitable contouring of the part load control edge.

of deceleration, and the several'steps, one for each injection, being separated by intervening periods or dwellst-:gtlien the pump plunger is motionless or substantially motionless.

-A curve illustrative of this time of plunger action is shown in Fig. 14, and in Fig. 15` thereV is illustrated a cam for effecting thistype of motion.l

Referring to Fig. 14, the ordinates of the dlagram represent pump stroke while the abscissae represent cam rotation in degrees. As indicated on the ngure, the scale of ordinates to absclssae is approximately three .to'one and the curve is for a cam of the kind suitable for a pump having` `four delivery periods per delivery stroke of the plunger. 0n the curve illustrated, the four delivery periods occur along the portions A, B, C, and D of the curve while the suction stroke is 5 represented by the dotted line portion E of the curve. The delivery periods are effected respectively by the rising portions A, B,'C, and D of the cam, these portions being separated by POrtions I, II and III of constant'radius which provide for 10 the intervals of no plunger movement between the several injection periods. While portions I, II, and III are most advantageously of constant radius, they are not necessarily so. The portion E of the cam profile provides for the suction 15 stroke. l

It will be evident that -the profile of the cam V may be varied to give a curve diierent in form from that just described, but the curve illustrated has been found to be advantageous for securing 20 good injection characteristics.

As will be observed from Figs. 14 and 15 the portion E of the profile of a cam suita* le for effecting a series of delivery periods fol icl delivery stroke, must be relatively steep, and this 25 results in a high speed suction stroke as well as a suction stroke of greater length than would be required for a plunger effecting but one delivery period. v For this reason the arrangement of the pump suction passage of the pump in line with 30 the cylinder bore, to provide for ilow of liquid into the pump chamber without abrupt change in direction, is highly advantageous.

It has been found desirable, in order to insure good delivery characteristics, to provide a 35 certain counter pressure on resistance to the overflow from the'several relief ports. This may be accomplished indifferent ways as is illustrated in Figs. 1, 16, and 17. As shown-in Fig. 1, a spring vloaded valve 18 opening in the direction of ver- 40 ow is provided to maintain a predetermined pressure load on the liquid overflowing through the passage 3|.

In the arrangement shown in Fig. 16, the over- -ow passage 34 has inserted therein a choke plug 45 80, the diameter of the orice of which will vof course determine ythe extent of the counter pres* sure developed byoverfiow. In Fig. 17 the'overdow passage is restricted by means of an adjustabi-e plug az, by means of which the value of the 5 resistance to overow may be varied as desired.

l In the arrangements shown in Figs. 16 and 17,

^ the overflow is returned directly tothe suction line 30 and when such direct return of the over- 55 flow to the suction line is effected, the return line -is advantageously provided as shown in these figures with an aiipgorjvapor collecting pocket 84 located at a high point in the return line and closed by a removable member such asplug 86 which may o from time to time be adjusted or removed to vent any air or incondensible gas vthat may have collected in the chamber. Obviously, the spring roaded ball valve construction shown in Fig. 1 may be embodied in a direct overflow return pas- 35 sageof the` kind yshown in Figs. 16 and 1'1 or the forms of choke shown in the latter figures may be incorporated in an independent overow line of the kind illustrated in Fig. 1.- Also, it will be evident that any individual relief passage may be 70' restricted to provide the desired counterpressure acting on the overflow.'

Referring now to Figs. 18 to 21, another forni'.A

vof pump embodying' the invention is shown, which?.

with respect-to that portion o f the pump illustrated in Fig. 18. 'I'his embodiment diiIers principally from that shown in Fig. 1 by the tact that the delivery and relief ports are not disposed in groups located in two longitudinally separate zones in the pump barrelfbut are located in the same zone, and diiierent portions oi one plunger recess provide both the plunger delivery port and the plunger overilow ports, avoiding the necessity for two longitudinally separated recesses as in the plunger shown in Fig. 1. One principal advantage of the pump shown in Fig. 18 is that the length of the pump barrel and plunger can be made substantially shorter than in the form shownin Fig. 1.

In the present arrangement, passages 34a. Mb, 34o, and 34d, which terminate at their inner ends respectively in the relief ports n to n, are bored directly through from the opposite side of the pump barrel 20a and communicate with an annuaassnso lAs in Fig. 8 the diagram, for simplicity, shows only two rather than four cylinder delivery ports,

and corresponding relief ports. The recess in the pump plunger in the present embodiment is shaped to provide control edges similar in nature and function to the control edges shown in Fig. 7 and need not again be described in detail. In

this instance, however. the portion of the recess in line with the cylinder delivery ports cli-d4 provides the plunger delivery port.

In position 22a the recess 48 is in communication with the delivery port d1 and is also in communication with the relief port r1 by way of the passage lsf. Upward movement of the lar reliefA passage Ae which in turn communi- Y plunger does not result in commencement of decates with the passage 34. The annular passage livery until position 22h is reached, in which posi- 34e is provided between the exterior or the pump tion passage 48f passes out of communication barrel and thel wall oi a recess I8 formed in the with port n. Delivery continues after position head portion Ita. o! the pump casing, the. pump 22h is passed until position 22e is reached, when barrel being 'held in position axially by means oi delivery is terminated by passage 48g coming into a nipple 22a threaded into the recess in the head, registration with port r1. As the plunger adand-suitably packed against leakage of overilow vances trom position 22e through positions 22d,l

liquid by packing` Il. The barrel is centered by 12e, and 22,1, passage 48g passes port ri, through one or more such as the one indicated at which overilow occurs \and during this period 20h and is restrained against turning movement passage 48! comes into communication with eby means of locating pins the recesses for which' lief -l10rt ra. By the time position 22g is reached,

are= shown at Ma in Flg.20.

In this embodiment the several cylinder delivery ports are at the same height in the pump barrel asfthe corresponding cylinder reliei! ports and as will be observed from Fig. 18, the bores IIb andV c for 'relief ports rz and n are carried throughto the opposite side of the bore to provide the corresponding delivery portssda andl da' which in turn communicate with the delivery passages 3l and 40. Ports da and da thus liein the same axial plane as the relief ports. Ports d1 and d4. as will be seen more clearly from Fig. 19, lie

the recess 48 has passed out of communication with delivery port .d1 and is in communication with delivery port dz. but delivery through the latter port does not commence until the plunger has reached the position 22h in which position the channel I8! passes out of communication withsreliei port rz.` Passage 48g has passed out A second delivery period occurs during movement of the plunger from position 22h .to position 22:'. When the latter position is reached, channel 48g in a plane at right angles to the pianey or ports da comes into communication with port r2 t0 terand da. Ports d1 and d4 and the transverse pasminate injection. During the remainder of the sages connecting them with their respective outlet plunger stroke, to position 22g', the overflow necespassages 36 and 42 are advantageously formed by sary t0 Permit this Continued movement iS continuationsoi auxiliary bores 82 and Il which provide openings through the barrel directly op- .d with port fr. As in the form describedin eiected by the continued registration of/ passage pomte and in line with these ports.. The auxiliary bores 92 and 84 may be closed by plugs in the saine manner that the auxiliary bores, the continuations oi which form portions oi! the overilow and delivery passages of Fig. 1, are closed by plugs 96, but as will hereinafter appear, thebores connection with Fig. 8, it will be apparent that the action Just described may be continued for additional cylinder ports placed, above those shown in Fig. 22.

In the diagram just described, the plunger is adjusted rotatlonally for full load operation. For eiecting part load operation, the plunger is vturned in the same mannerwas has previously As willbe more clearly apparent from Figs. 20 been described in connection with the pump and 21, the delivery es It and I2 lie close shown in Fig. 1 and the desired timing of part together on the same` radial line where they load delivery may be effected in the present ememerge from the top o! the barrel and passages bodiment, as in the -previously described embodi- 3l and lo lie close together on a second radial ment, by suitably shaping the part load control line at right angles to the nrst line. where they emerge from the top oi' the barrel. In order to symmetrically locate the pump outlets and to 'provide room for the several discharge valves. the head portion of the pump casingis advantageously arranged in the same manner as shown in Fig. 3 and the portions of the outlet passages in the head are brought intokcommunication with the portions in the barrel by means of two channels Ilb and l!!! which respectively provide communication between the portionsoi channels 40 and I2 in the head and in the barrel gether with the control recess and edge portion.

ot the pump plunger.

A s will be seen from this ligure, which has been shown with the plunger adjusted for partI load operation after having covered port r1 and the port formed by the bore 92, the control edge 49h covered bore 92 before edge 49e covered relief port r1 to start delivery through port di.

From the figure it will further be apparent that bore 92, which would if open act as a relief channel, will not be opened on further movement of the pump plunger before the relief port r1 is opened, since edge 49d will pass both of these ports at the same time. If the plunger is turned to full load position, that is, moved to the left in FigF 23 so thatthe edge 49h is in line with the line of relief ports, it will'be evident that-this edge will close port 92 as soon or sooner than the relief'yport r1. Stated in another way," the bore 92 will, in all positions of adjustment of the pump plunger, be covered for a period as long or longer than the period when relief port r1 is covered, so that bore 92 can never have any effect on or in any way interfere with the timingL of the delivery period through port di, regardless of the position oi adjustment of the plunger with respect to load. Likewise, port 94 can in no way aect the delivery period through port d4, which is controlled by the covering and uncovering of the relief port r4.

With the passages in the pump barrel disposed as above described, it will be apparent that all of the transverse passages for both delivery and overflowv may very easily and readily be made' tration has been applied to a pump of the general `type shown in Fig. 18 ih which the relief and delivery ports are located in the same zone along the length of the barrel. It is of course equally applicable to the type of pump shown in Fig. 1.

In this embodiment, the barrel 29h is clamped to the head portion I9b of the pump casing by meansA of a threaded collar 2211i In the present' form only a shallow cup-like recessforthe reception ofA the plunger head 26a which is held in position by the retaining washer 94a. The tappet is restrained against turning by any suitable means such for example as a locating pin working in a vertical slot in the tappet, or by a an arcuate slot 16a in the tappet in the same manner as in the construction shown in Figs. 1 and 2.

The tappet and plunger are in this instance loaded by means of two heavy helical springs 99 and 99a concentrically arranged between the retaining washer and shoulderedportions of. the barrel structure. The use of the additional Vand comparatively large diametered spring 99a is made possible in the present instance because of the fact that4 the turning means for the plunger is located above rather than around the tappet so that the springs do not have to extend downwardly into the tappet and consequently have available a space of larger diameter than would be the case with the construction shown in Fig. 1V and with a tappet of equal cross-sectional dimensions. Thus, in the form shown in the present figure, a more powerful spring loading can be obtained without having to enlarge this portion of the pump structure.

From the foregoing description it will be evident'that in accordance with the present invention a single barreled pumpstructure can be provided which is relatively cheap to` manufacture as compared with multiple plunger 4pumps and which will at the same time be capable of supplying fuel accurately and in an accurately adjusted quantity to a Vplurality of separate outlets. Because of the fact that control of the timing ofthe beginning and ending 'of each delivery period is effected by a single plunger cooperating with denitely positioned ports, the

possibility of variation between the quantitiesV delivered to any two different outlets is substantially eliminated, regardless of the position of adjustment of the plunger with respect to load and also regardless of wear on the pump. If the pump cylinder and barrel'wears, the tendency of such wear is to affect all deliveries to the same extent, which is .not true of multiple cylinder pumps where wear of unequal magnitude fre-y quently occurs as between different pump plung ers and cylinders. Furthermore, since one pump plunger and cylinder assembly serve to effect a multiplicity of deliveries, the manufacture of each pump and cylinder assembly is facilitated -because of the fact that the exactness -of the matching of the dimensions of cylinder' bore and plunger diameter, required for the di'erent pump units of a multiple pump, is not required.

In Figures 25 to 36, inclusive, further di'erent forms of plunger and barrel construction are illustrated, which provide for regulation of the de-V livery of the fuel from the pump chamber to the delivery conduits in various different manners from that which has been described. In order to illustrate these different forms of pump plunger and. barrel arrangements, diagrams similar to,

those of Figs. 8 to 10, 22 and 23 have been employed, since the remainder of the pump construction may be the same as shown in Figs. 1, 18 or 24. For the sakeof simplicity, only so much will be described in detail with reference to the additional figures asdiii'ers from the structures heretofore described. i

The arrangement shown i Fig. 25 differs 'from the previously described embodiments'in the location and arrangement oi' the relief or overow ports in the barrel, with respect to the plunger overilow ports. Referring now to the ligure it will be observed that the plunger 26 is of the lform illustrated in Fig. 8 in which a separate plunger delivery recess 46 and aplung'er overflow recess 48 are provided.` In the present instance two delivery ports d1. dz are shown', and three termination of a delivery period.

' overflow p orts r1, r2, and ra are provided.' 'I'he plunger has been shown in two positions c and d corresponding to positions c and d of Fig. 8 and illustrating respectively the commencement-and As will be observed from position livery period through. -port di is about to commence, slnc'e the upper 'control edge 48h ot the control projection 48' is just passing out oi' communication with the overflow port 'rr to terminate overflow by way of the plunger overiiow port'4lf. In this position the delivery recess 4l has already moved into communication with port di. -As the plunger moves from the position c to the position d, vdelivery is eilected in the manner previously described in connection with Fig. 8 but vthe. delivery period through port' di is, in the present instance, terminated when the plunger reaches position `d by the control edge-48a of the 20 recess 48 passing the lower edge'of the relief port n so that overflow takes place due to communication between the plunger overow port 48! and the overflow port rz. This takes place before the plunger overflow port 48g cornesinto communication with port r1. It will be evident that by similar action. delivery through portda will be commenced by plunger port' 48fpassing beyond overflow port rz and will be terminated by port 4l! coming into communication with port n.

As willbe seen from the above, this arrangement differs from the arrangement illustrated in Fig. 8 by the. fact that commencement and termination of a delivery period is in the present 35 case determined by the action of a single plunger l overflow port in conjunction with two cylinder overow ports, whereas in the arrangement shown in Fig. 8 commencement and termination of a delivery period are determined by the'action of two' dinerent plunger overflow ports acting in conjunction with the same cylinder overflow port. In some cases the present arrange-` ment has proved useful rather than the arrangement illustrated in Fig. 8.'

In the arrangement shown in Fig. 26, the location of 'cylinder delivery ports and cylinder overflow ports with reference'to each other and to the plungerports is such as to provide a certain degree of precompression of the fuel in the pump chamber before delivery is commenced so that for each delivery period, high pressure delivery from the very instant of commencement of the delivery period may be insured.

Referring now to Eig; 26, the plunger is of the general form shown in Fig. 8 but Ywith the in.-

clination of the part load .overnow control edge 48o the same Vas in Fig. 12. The arrangement further is similar to that shown'i'n Fig. 8 in that the commencement and .ending of the delivery 00 periods is effected by plunger portsllf and 48g cooperating with the same overflow port rather than by the arrangementshown in Fig. 25. In Fig. 26-positionsc and d have also been shown corresponding, in' so far as termination and end 05 ing of overilow are concerned, to positions c and d of Fig. 8. As will be observed from position l28e, the plunger overnow port Ilias just passed out of communication with the relief port rr so that the liquid is at this point trapped in the pump chamber Il. In the present arrangement it. be noted, however, that the plunger delivery port 4i. is not yet in communication with the delivery port d1 andl consequently compression of the trapped liquidis effected by moveu ment of tle plungcr from position c to position c'. In the latter position the upper edge 46a of the plunger delivery port passes the lower edge' of port di to commence the delivery period, and delivery continues through'port di until overflow is again established by registry of plunger port 5 25e, the de- 4lawith overilow port n.

In similar manner, precompression for the delivery period Ythrough port dz is eilected by port v-481 passing; out of communication with port r2 `before the plunger delivery port 46"comes into communication with port dz.

In-the embodiment illustrated in Fig. 26, the .amount of precompression is constant regardless of the rotational position of the plunger for load adiustment Variation of the degree of precompression with variations in load adjustment may, however. be readily accomplished as illustrated in Figs. 271' and 28. J,

In the form shownin Fig. 27 the upper and lower control edges 48a and 46h respectively of the plunger delivery recess 46 are in planes normal to the axis of reciprocation of the plunger 28. as in the forms previously described, and consequen'tly communication between the plunger overflow port and any given delivery port will be established and cut oi! in the same stroke positions of the plunger regardless of its position of rotation.

Unlike the previous embodiments, however, the present form provides inclined edges- 48a, 48h, "d, and 48e so that the channels providing the plunger overilow ports 48j and 48g are inclined. LWith these ports thus inclined it will be yevident that anygiven overflow period will be commenced and terminated in different stroke positions ot the plunger for different positions of rotational adjustment thereof. In the figure, the plunger is illustrated with the overflow port 48f .lust passingout of communication with the4 overow port ra to start precompression prior to registration of port 48 with port da." It will be y seen from the figure that if the plunger is turned to-reduce the quantity delivered, that is, so that the control edge 48e movesI to the left from the position shown in the figure, the plungerport 48j will pass out o! communication with the overow port n in a lower stroke position of the plunger" than the. position shown in the drawing. This'evidently will result ina higher degree of precompression of the fuel before delivery )through the port dz can take place since the pump plunger must travel a greater distance during the interim between the cut-off of overilow and the registration of the delivery ports.

Thus iig/'will be seen that with this arrangement, the degree of precompression increases with adjustment for. decrease in load and decreases with adjustment for increase in load.

Variation in the degree of precompression for dierent load values may also be accomplished so as shown in Fig. 28 in which ligure the overflow control edges 48a, 48h, 48d, and 48e are in planes normal to the axis of recprocation of the plunger so that the times of beginning and. ending of 'the overflow periods remain constant with respect to the stroke position of the plunger regardless of the rotational position of adjustment of'the latter; In the present instance control edges 48a and 4Gb of the delivery port 46 are inclined, and in order to illustrate the different ways in which the relationbetween degree of' -precompression with respect to load may be varied. the ledges oi the' delivery port have in this form en illustrated as inclined in such 4 manner as to' produce increase in the value of u precomprssion upon adjustment to increase the load, which is the reverse of the variation obtained with the form shown in Fig. 27. In Fig.

28 the plunger is again shown with the overflow through port n just being terminated to start the precompression period, the position of adjustment of the plunger being for full load. Ii

now the plunger is turned to bring the control edge 48c into play, it will be evident that a 10 higher portion of the control edge 46a will be in axial alignment with the delivery port d2 and consequently less plunger movement will be required after overflow ceases in order to bring the delivery port 46 into communicationy with the cylinder port d2. This obviously will result in less precompression.

It will be evident from the embodiment shown in Figs. 27 and 28 that increase in the degree of precompressicn with either increase in load or decrease in load may be obtained as desired by proper sloping, in either case, of the control edges of either the plunger delivery port or the plunger overflow ports, or both. In the forms illustrated in Figs. 27 and 28, the shape of the control projection 48' is such as to .provide for constant commencement and variable termination of injection with respect to the pump cycle in the manner previously described in connection with Fig. l2, but this obviously may be varied.

The character of overflow control effected by means of the island-like control projection 48',

described vin the previously discussed embodi ments, can also as readily be obtained by means of a recess in the pump plunger as illustrated by the embodiment shown in Fig. 29.`l In this embodiment the plunger is provided with an overnow recess I8 and an inclined control edge 48e," and a lower control edge llef'. These edges between them vprovide an overflow channel 48g". The positions of the plunger shown at c and d correspond respectively to positions c and d of Fig. 25 and illustrate the commencement 'and termination of an injection period. In position c the plunger overflow port is just passing out of communication with overflow port r1 to start the delivery'period through port d1. This delivery period is terminated when position d is reached, in which position port 48a comes into communication with the overilow port rz; In the embodiments illustrated in Figs. .30 to 34, the various features illustrated inFigs. 25 to 29 are shown applied to pumps having plungers of the type shown in Fig. 18, which have but one recess, the general action of which pumps has been describedIin detail in connection with Figi ures 18 and 22.

Fig. 29 illustrates the action with this type of plunger when a single plunger Voverilow port, acting in conjunction with two cylinder overflow 60 ports, determines th commencement and ending of a delivery period. Position b of Fig. 30 shows the plunger in the position wheredelivery through port di is commencing due to port 8f Apassing out of communication with port mand 65 position c illustrates the termination of' this delivery period which is caused by port f coming into communication with port n.

' Fig.A 31 illustrates a variation in vwhich a single plunger overflow port 'laf is provided rather 70 than two spaced ports I8! and 48g as ir the previously described embodiment. In position b'the port l8f has just passed out of communication with overilow port n to commence delivery through port d1, this delivery period being ter- 76 minated by port f registering with port rz,

ment illustrated in Fig. 26.

as shown in position c. By the time port f has closed port rz by passing out of communication with this port as illustrated by position d, the plunger port is in communication with the delivery port d2 and the second delivery 'period commences, continuing until the position e is reached when port 8f comes into communication with overflow port rs. It will be evident that turning the plunger to bring the inclined control edge 48o into action will vary the duration of the delivery peri^ds in the same general manner previously described.

Fig. 32 shows a construction producing action corresponding to that produced by the form shown in Fig. 29. In Fig.` 32, position b again shows delivery commencing through port di due to portlf passing out of communication with port r1, and position c shows the ending of the delivery period, caused by port 48j' coming into communication with port rz. The action taking place in Fig. 32l as compared with that taking place in Fig. 31 is different in that in Fig. 32 termination of the delivery period is varied with respect to the pump cycle with different load adjustments of the plunger. whereas in Fig. 31 the commencement of the delivery period is varied with respect tothe pump cycle as the position o1 the pump plunger is adjusted for different loads.

In the embodiment illustrated in Figs. 33 \and 34, an arrangement is shown for producing precompression with a plunger having a single recess and functioning similarly to the arrange- Fig. 33 shows the plunger and barrel in diagrammatic section while Fig. 34 shows the surfaces developed into a plane view. In this arrangement the bottom edge 48e of the plunger recess 48 is in a plane normal to the axis of reciprocation of the plunger while the upper edge 48a is provided with an onset portion 48a into which the control projection 48 extends, so that the plunger overilow port lsf is at adierent level from that ofthe delivery port provided by the main portion of the recess Il. As will be evident from Fig. 33, the control port 8f passes out of communication with the overflow port r1 before the edge 48a reaches the delivery port d1, thus providing for a period of precompression before the latter port is uncovered. Evidently the same action will take place on the next delivery period when the control projection 48' will cover the port'rz before the edge launcovers the delivery port da.

Variation of precompression for different load adjustmentsV of the pump may also readily be accomplished'with this general arrangement as iilustrated bythe embodiment shown in Figs. 35 and4 36. This arrangement is the same as described in connection with Figs. 33 and 34 except 'that the edges '48a' andlb are inclined to provide between them an inclined overow port passage 48f-'. As will be clearly evident from Fig. 6, rotational movement of the plunger will operate Kto vary the amount of plunger travel required between the position when an overow portV is covered by the projection 48 andthe position when the next cylinder delivery port is opened.

While in Figs. 35 andy 36 the slopeof the port 48f' has been shown such that a greater degree of precompression is effected as adjustment is made for lower load, it will be obvious that the inclination of this port may be made in the opposite direction to produce the opposite relationship between the degree of precompression and Also, while the preferred form of ports. has

been described and illustrated, lnwhlon the cylinder delivery ports are circular and the plungery delivery ports are elongated, it will be evident that the same function is readily obtainable by utilizing circular plunger delivery ports and 20 -elongated cylinder delivery ports.

In all of the previously described embodiments, the cyl-.inder delivery'ports are longitudinally spaced, but a longitudinal spacing of the delivery ports is not required in order to provide an operative pump embodying the principles of the invention.

The cylinder delivery ports may be circumferentially spaced at. the same level but when this is done modification oi' the form of the plunger is required in order to secure the proper cooperative action'between the ports.

In order to illustrate how the cylinder delivery ports may be placed at the same level, Figs. 37 and 38 show in section and developed view, respectively, an arrangement of this kind. Referring now to these figures, which for the sake of simplicity show only two delivery outlets, the cylinder delivery ports di and da are circumferentially spaced but at the same level -in the pump barrel. 'Ihe cylinder overflow ports r1 and rz are longitudinally spaced as in the previously,described embodiments, and in the present instance the plunger is provided with a recess 48 in which is located the projection 48 providing an inclined control edge 48e and plunger overflow ports 481* and 48g. The construction of this part of the pump plunger is similar to that shown and described in Fig. 22. In the present.

the recess. Port 48d is placed in communication with ,the pump chamber by the transverse bore B2b which also communicates with the recess 48.

wthe'overflow ports r1 and 48j are in communica-- ion and by the time these ports have passed out of communication,.th e delivery port 48h. will have been brought into communication with the f `delivery port d1. As the plunger moves up- Wardly. delivery will take place through port di until registration between overflow port 48g and r1 takes place. During this delivery od no delivery will be effected through the delivery port d2 since port 46c is circumierentially offset .from port dz. By the time the plunger overflow In the position of. the parts shown` in Fig. 37

. port 48j has passed out of registration with port r2 to commence a second delivery period, port 46c will have passed out of communication with port di and port 46d will be in registration with port d2. 'Ihe second delivery period is thus eilected 5 through the latter port. It will be apparent that \more than two cylinder delivery ports may be placed in circumferentially spaced relation at the same level and the'action just described be secured for more delivery periods by providing 10 the -requisite number of separate longitudinally spaced and circumferentially offset delivery ports in the plunger. k

Regulation of the quantities supplied to the various delivery ports is eiected n the same 15 manner as in the previously described embodiments, by turning the plunger so that the control edge cuts off the overflow at different points in the plunger stroke. From Fig. 38 it will be evident that the plunger delivery ports 46c and 2Q 46d must have suiiiclent width in peripheral diection to register with their respectively cooperating cylinder .delivery ports in any position of rotation of the plunger within the range of turning vmovement required of it to effect the 25 desired regulation. As will be apparent from Figs. 37 and 38, the construction just described requires a more intricate form of plunger than the previously described embodiments, butin some instances this 30 form of construction may be preferable to one in which the delivery ports are longitudinally spaced.v 4 y,

Referring now to the pump shown in Fig. 39 r and related figures, the type of pump illustrated 3 differs from the various forms hereinbefore described principally in the construction of the plunger and the porting arrangements provided by the plunger and barrel for eil'ecting the desired 'character ofoperation. This difference consists 40 principally in the ifact that instead of having a plurality oi' cylinder overflow ports in the barrel, a single cylinder overflow port is employed with 'which a plurality of plunger overiiow ports havlng control edges come into communication in 45 sequence during the discharge stroke oi the plunger to provide for overflow periods, the timing and duration of which determine the timing and duration of the delivery periods.l

Since the general organization of pump con- 50- struction, aside from the form of the plunger and the porting arrangements, may be the same as in the embodiments previously described, the description of this form of the pump will be connned to the portions thereof embodying the parts 55 diierent from those previously described, it being understood that in so far as the present construction is concerned any of the various features of cam'and tappet construction, plunger control, overiiow resistance, and special modes of boring 60 the barrel to provide the desired porting thereof, which have previously been described, may .be incorporated.` j

As shown in Fig. '39, the pump barrel |20 is secured to the pump head ||6 by means of the 65 cap nut |22 and is provided with delivery ports di, dz, dp, and d4 connecting respectively to the discharge passages |38, |38, |40, and |42.

The delivery ports are longitudinally spaced in the barrel and circumferentially oii'set from 7.0 each other. The barrel is further provided with an overilow or relief passage |34, which passage terminates in a single relief port r.

'Ihe plunger in this instance is provided with a circumferentially extending recess |46 which 75 

